Turbomachine



R. COESTER TURBOMACHINE May 8, 1962 2 Sheets-Sheet 1 Filed May 8, 1957INVENITOR. z 5 e 2' Gear/ r y 1962 R. COESTER 3,033,441

TURBOMACHINE Filed y 1957 2 Sheets-Sheet 2 Fig. 3

IN VEN TOR.

72 m 63/"- BY United States Patent ()fiflce 3,033,441 Patented May 8,1962 3,033,441 TURBOMACHINE Robert Coaster, Znmikon, Zurich,Switzerland, assignor to Maschinenfahrik Benninger A.-G., Uzwill, SanktGallen, Switzerland, a Swiss company Filed May 8, 1957, Ser. No. 657,846Claims priority, application Switzerland May 8, 1956 2 Claims. (Cl.230-425) The present invention relates to a pressure generatingturbomachine and in particular to a transverse flow blower in which aspace is by means of a feed rotor divided into a high pressure and a lowpressure. The invention has for its object to improve the efliciency ofturbomachines and to increase the specific feed pressure in particularat small specific quantities delivered.

It is known that transverse flow blowers in which the rotor is shieldedby a closely fitting housing wall between the outlet of the highpressure chamber and the inlet of the low pressure chamber achievecomparatively high efficiency at high quantities supplied. With smallerquantities supplied, however, pressure and efliciency drop considerably.The determining factor is the undimensional coetiicient in which Q isthe quantity delivered, D the rotor diameter, b the rotor width in axialdirection of the rotor and u the circumferential speed of the rotorperiphery. Small coefficients are frequently desirable, such as in fanunits where the flow rates are required to be as low as possible, or inblowers and pumps for small deliveries compared to the feed pressure.

It has been suggested to return part of the medium delivered from therotor into the latter between the outlet of the high pressure chamberand the inlet of the low pressure chamber since experience has shownthat the flow in the rotor is somewhat improved, particularly withcoeificients (p smaller than approximately .5. The present inventionrelates to means substantially increasing pressure and efliciency overthat of known turbomachines and partly displaying purely structuraladvantages for reasons disclosed below.

According to the present invention means are provided which cause thepressure on the rotor periphery to be increased at least substantiallyat the place where the rotor blades enter the low pressure chamber.

An embodiment of the invention is described in conjunction with theattached drawings in which:

FIG. 1 is a diagrammatic cross-section of a turboblower to illustratethe operation or" the arrangement according to this invention;

FIG. 2 is a cross-section of a turboblower with a device enabling astabilizing jet to be generated by means of a separate source ofpressure; and

FIG. 3 is a cross-section of a turboblower in which the configuration ofthe inner housing wall is selected so that the jet is generated by theinner wall.

FIG. 1 is a cross-section of a turbomachine known as a transverse flowblower. By means of a blower rotor 10, the blower is divided into twochambers 12 and 13 along lines parallel to the axis of the rotor wherethe walls closely approach the rotor as shown in FIG. 1. Blower rotor Itconsists of sheaves 14 the circumference of which has connected theretoblades 15 mounted at a certain angle and spaced apart circumferentiallyless than their dimension radially of the rotor. The air enteringchamber 13 on rotation of the rotor does not at first have the fullpressure but an increased speed which is transformed into pressure inthe course of the flow. The

front chamber 12 will therefore be termed low pressure chamber, the nextfollowing chamber in the direction of flow, high pressure chamber 13.

In order to explain the invention, it is assumed that the rotor iscovered from point 17, where the blades leave the high pressure chamber,to point 16, where the blades enter the low pressure chamber, i.e. thatspace 18 is filled or not provided.

It has been found that a substantial increase in pressure and efiiciencycan be obtained in transverse flow blowers if a jet bound at itscircumference and having a static pressure and a total pressure raisedrelative to the condition in the low pressure chamber, is supplied atleast substantially at the place of entry of the rotor periphery intothe low pressure chamber, for the following reasons:

A fluid flow entering the rotor at point 1 from the low pressure chamberis accelerated in the circumferential direction of the rotor by therotor blades and leaves them approximately at point 2. For reasons ofcontinuity, as much fluid must emerge at point 3 of the blade channel ashas entered at point 1, at least while the flow rates do not approachthe velocity of sound. This is possible without substantial disturbanceif a fluid flow containing the necessary quantity of fluid enters therotor at point 4 as well. For this latter fluid flow, the sameconditions will apply. Its passage through the rotor can, however, beforced by applying the fluid flow to point 4 under elevated pressure. Itis thus possible to limit the quantity of medium supplied to the rotorto a minimum. A jet width of a maximum of 3.56 with 5 as the angle atwhich a rotor blade appears when viewed from the axis. The value 3.56 iscritical. It is obvious that the auxiliary jet should preferably beapplied substantially radially inwardly.

In order to obtain such an auxiliary jet, a duct 18 is provided which isconnected, on the one hand, with the high pressure chamber and endsapproximately at the point where the rotor blades 15 enter the lowpressure chamber. This point is approximately identical with the,

said point 4. At the end of duct 18, a nozzle-type device (not shown)may be provided; it is also possible to baflle the medium enteringthrough duct 18 at the transverse wall 6 and thus to obtain aparticularly advantageous distribution of velocity since the speed ofentry into the rotor in the vicinity of the transverse wall 6 is highestand then gradually decreases. Moreover, there exists the possibility ofconnecting the duct '18 with a separate source of pressure and therebyto obtain the auxiliary jet.

Without this auxiliary jet the flow directed at the rotor in the lowpressure chamber seen in the direction of rotation can be obtained onlygradually and the more slowly, the smaller the total throughput or thevolume coefiicient (p is. A wider or narrower zone with a lesser flow iscreated in which the losses due to unfavourable flow angles and owing tocirculation are substantially larger than the losses unavoidable in theapplication of the auxiliary jet according to this invention.

As further shown in FIG. 1, the duct 18 can be formed by covering theportion of the rotor projecting into the high pressure chamber by meansof a body 20 so that duct 18 is formed above the said body. The airsupplied by the blower flows to the right in the high pressure chamherwhen the direction of rotation is as indicated, while owing to theelevated pressure in chamber 13 a return flow is obtained through theupper duct 18. This causes the transverse wall 6 to perform a dammingaction whereby the jet stabilizing the main flow in the manner describedis produced.

The angle at which the duct 18 appears at the rotor periphery seen fromthe rotor axis is most favourable if it is .5 to 3.5 times the value ofangle 6, i.e. the angle at which a rotor blade appears when viewed fromthe axis of rotation. This angle is preferably below 30.

FIG. 2 shows an embodiment in which the jet according to the inventionis produced by a separate source of pressure, by way of example afurther compressor. In the turbomachine here shown a tube 26 providedwith nozzles or slots 29 is arranged at the point of entry of the rotorparallel with the axis of rotation. This tube permits a rise ofpressure, by way of example in the magnitude of one-third to one-half ofthe stage pressure differential, to be produced at the shown point ofentry of the rotor into the low pressure chamber. The high pressure intube 26 relative to the underpressure chamber is produced by a separatesource of pressure.

FIG. 3 shows an embodiment in which a pressure surge at the point ofentry of the rotor into the low pressure chamber is generated solely bythe configuration of the inner housing wall. If a transverse wall 25 isprovided at the partition between high pressure and low pressurechambers, the air, which returns at all events, is baflled so that apressure surge due to the damrning effect is obtained. It should benoted that a largely free supply is possible to this transverse wall orpartition. The transverse wall should be inclined towards the rotorradius at the point of entry of the rotor into the low pressure chamberby not more than 30 at the end of the said radius (angle 5 in FIG. 3).To adapt the housing to the flow, the transverse wall may be somewhatless inclined with increasing distance from the point of rotation.

Having now particularly described and ascertained the nature of my saidinvention and in what manner the same is to be performed, I declare thatWhat I claim is:

1. In a transverse fiow blower, a housing comprising spaced walls, arotor mounted in said housing for rotation about an axis parallel tosaid walls, said walls extending closely adjacent said rotor along twocircumferentially spaced axial lines so as to separate low and highpressure chambers on opposite sides of said rotor, said rotor havingblades on its periphery spaced a less distance than their radialdimension and arranged parallel to the axis of rotation and forwardlyinclined at an angle to a radial plane so that said blades form a hollowspace within said rotor, said rotor rotating in a forward direction sothat fiuid enters said rotor from between said walls to form said lowpressure chamber and is discharged on the other side between said wallswhich confine said fluid to form said high pressure chamber, the wall ofsaid housing adjacent said rotor at the axial line at the entry of itsperiphery into said low pressure chamber extending away from saidperiphery at an angle not greater than 30 to a radial plane at said lineof entry to form an abutment facing said high pressure chamber, saidwall from said abutment extending in a smooth curve to the wall of saidhigh pressure chamber and spaced outwardly of said rotor, a second wallspaced inwardly of said first wall and extending closely adjacent theperiphery of said rotor for a substantial portion of said periphery fromsaid high pressure chamber toward said abutment and having a smooth,continuous uter surface to form with said wall from said abutment a ductbetween said walls extending from said high pressure chamber beyond saidrotor to the line of entry of the periphery of said rotor into said lowpressure chamber, said abutment and the adjacent end of said second wallbeing spaced at greater distance than the space between adjacent bladesand less than said Walls of said duct at said high pressure chamber andforming the outlet of said duct to direct a flow of fluid under pressurefrom said high pressure chamber in a generally radial direction betweenthe blades of said rotor at its line of entry into said low pressurechamber.

2. The apparatus defined in claim 1, in which the spacing of saidabutment and the adjacent end of said second wall subtends an angle atthe center of the rotor not greater than 3.5 times the angle subtendedby the circumferential space between adjacent blades.

References Cited in the file of this patent UNITED STATES PATENTS507,445 Mortier Oct. 24, 1893 846,896 Becker Mar. 12, 1907 1,045,732Nash Nov. 26, 1912 1,429,044 Nash Sept. 12, 1922 2,537,344 Gruss Jan. 9,1951 FOREIGN PATENTS 158,915 Switzerland Feb. 16, 1953 291,007 GreatBritain Aug. 21, 1928 373,998 France May 31, 1907 477,345 Germany June12, 1929

